
package lucee.runtime.jsr223;

import java.io.Reader;

import javax.script.Bindings;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptException;
import javax.script.SimpleScriptContext;

/**
 * Provides a standard implementation for several of the variants of the <code>eval</code> method.
 * <br>
 * <br>
 * <code><b>eval(Reader)</b></code>
 * <p>
 * <code><b>eval(String)</b></code>
 * <p>
 * <code><b>eval(String, Bindings)</b></code>
 * <p>
 * <code><b>eval(Reader, Bindings)</b></code> <br>
 * <br>
 * are implemented using the abstract methods <br>
 * <br>
 * <code><b>eval(Reader,ScriptContext)</b></code> or <code><b>eval(String, ScriptContext)</b></code>
 * <br>
 * <br>
 * with a <code>SimpleScriptContext</code>. <br>
 * <br>
 * A <code>SimpleScriptContext</code> is used as the default <code>ScriptContext</code> of the
 * <code>AbstractScriptEngine</code>..
 *
 * @author Mike Grogan
 * @since 1.6
 */
public abstract class AbstractScriptEngine implements ScriptEngine {

	/**
	 * The default <code>ScriptContext</code> of this <code>AbstractScriptEngine</code>.
	 */

	protected ScriptContext context;

	/**
	 * Creates a new instance of AbstractScriptEngine using a <code>SimpleScriptContext</code> as its
	 * default <code>ScriptContext</code>.
	 */
	public AbstractScriptEngine() {

		context = new SimpleScriptContext();

	}

	/**
	 * Sets the value of the protected <code>context</code> field to the specified
	 * <code>ScriptContext</code>.
	 *
	 * @param ctxt The specified <code>ScriptContext</code>.
	 * @throws NullPointerException if ctxt is null.
	 */
	@Override
	public void setContext(ScriptContext ctxt) {
		if (ctxt == null) {
			throw new NullPointerException("null context");
		}
		context = ctxt;
	}

	/**
	 * Returns the value of the protected <code>context</code> field.
	 *
	 * @return The value of the protected <code>context</code> field.
	 */
	@Override
	public ScriptContext getContext() {
		return context;
	}

	/**
	 * Returns the <code>Bindings</code> with the specified scope value in the protected
	 * <code>context</code> field.
	 *
	 * @param scope The specified scope
	 *
	 * @return The corresponding <code>Bindings</code>.
	 *
	 * @throws IllegalArgumentException if the value of scope is invalid for the type the protected
	 *             <code>context</code> field.
	 */
	@Override
	public Bindings getBindings(int scope) {

		if (scope == ScriptContext.GLOBAL_SCOPE) {
			return context.getBindings(ScriptContext.GLOBAL_SCOPE);
		}
		else if (scope == ScriptContext.ENGINE_SCOPE) {
			return context.getBindings(ScriptContext.ENGINE_SCOPE);
		}
		else {
			throw new IllegalArgumentException("Invalid scope value.");
		}
	}

	/**
	 * Sets the <code>Bindings</code> with the corresponding scope value in the <code>context</code>
	 * field.
	 *
	 * @param bindings The specified <code>Bindings</code>.
	 * @param scope The specified scope.
	 *
	 * @throws IllegalArgumentException if the value of scope is invalid for the type the
	 *             <code>context</code> field.
	 * @throws NullPointerException if the bindings is null and the scope is
	 *             <code>ScriptContext.ENGINE_SCOPE</code>
	 */
	@Override
	public void setBindings(Bindings bindings, int scope) {
		if (scope == ScriptContext.GLOBAL_SCOPE) {
			context.setBindings(bindings, ScriptContext.GLOBAL_SCOPE);
		}
		else if (scope == ScriptContext.ENGINE_SCOPE) {
			context.setBindings(bindings, ScriptContext.ENGINE_SCOPE);
		}
		else {
			throw new IllegalArgumentException("Invalid scope value.");
		}
	}

	/**
	 * Sets the specified value with the specified key in the <code>ENGINE_SCOPE</code>
	 * <code>Bindings</code> of the protected <code>context</code> field.
	 *
	 * @param key The specified key.
	 * @param value The specified value.
	 *
	 * @throws NullPointerException if key is null.
	 * @throws IllegalArgumentException if key is empty.
	 */
	@Override
	public void put(String key, Object value) {

		Bindings nn = getBindings(ScriptContext.ENGINE_SCOPE);
		if (nn != null) {
			nn.put(key, value);
		}

	}

	/**
	 * Gets the value for the specified key in the <code>ENGINE_SCOPE</code> of the protected
	 * <code>context</code> field.
	 *
	 * @return The value for the specified key.
	 *
	 * @throws NullPointerException if key is null.
	 * @throws IllegalArgumentException if key is empty.
	 */
	@Override
	public Object get(String key) {

		Bindings nn = getBindings(ScriptContext.ENGINE_SCOPE);
		if (nn != null) {
			return nn.get(key);
		}

		return null;
	}

	/**
	 * <code>eval(Reader, Bindings)</code> calls the abstract <code>eval(Reader, ScriptContext)</code>
	 * method, passing it a <code>ScriptContext</code> whose Reader, Writers and Bindings for scopes
	 * other that <code>ENGINE_SCOPE</code> are identical to those members of the protected
	 * <code>context</code> field. The specified <code>Bindings</code> is used instead of the
	 * <code>ENGINE_SCOPE</code>
	 *
	 * <code>Bindings</code> of the <code>context</code> field.
	 *
	 * @param reader A <code>Reader</code> containing the source of the script.
	 * @param bindings A <code>Bindings</code> to use for the <code>ENGINE_SCOPE</code> while the script
	 *            executes.
	 *
	 * @return The return value from <code>eval(Reader, ScriptContext)</code>
	 * @throws ScriptException if an error occurs in script.
	 * @throws NullPointerException if any of the parameters is null.
	 */
	@Override
	public Object eval(Reader reader, Bindings bindings) throws ScriptException {

		ScriptContext ctxt = getScriptContext(bindings);

		return eval(reader, ctxt);
	}

	/**
	 * Same as <code>eval(Reader, Bindings)</code> except that the abstract
	 * <code>eval(String, ScriptContext)</code> is used.
	 *
	 * @param script A <code>String</code> containing the source of the script.
	 *
	 * @param bindings A <code>Bindings</code> to use as the <code>ENGINE_SCOPE</code> while the script
	 *            executes.
	 *
	 * @return The return value from <code>eval(String, ScriptContext)</code>
	 * @throws ScriptException if an error occurs in script.
	 * @throws NullPointerException if any of the parameters is null.
	 */
	@Override
	public Object eval(String script, Bindings bindings) throws ScriptException {

		ScriptContext ctxt = getScriptContext(bindings);

		return eval(script, ctxt);
	}

	/**
	 * <code>eval(Reader)</code> calls the abstract <code>eval(Reader, ScriptContext)</code> passing the
	 * value of the <code>context</code> field.
	 *
	 * @param reader A <code>Reader</code> containing the source of the script.
	 * @return The return value from <code>eval(Reader, ScriptContext)</code>
	 * @throws ScriptException if an error occurs in script.
	 * @throws NullPointerException if any of the parameters is null.
	 */
	@Override
	public Object eval(Reader reader) throws ScriptException {

		return eval(reader, context);
	}

	/**
	 * Same as <code>eval(Reader)</code> except that the abstract
	 * <code>eval(String, ScriptContext)</code> is used.
	 *
	 * @param script A <code>String</code> containing the source of the script.
	 * @return The return value from <code>eval(String, ScriptContext)</code>
	 * @throws ScriptException if an error occurrs in script.
	 * @throws NullPointerException if any of the parameters is null.
	 */
	@Override
	public Object eval(String script) throws ScriptException {

		return eval(script, context);
	}

	/**
	 * Returns a <code>SimpleScriptContext</code>. The <code>SimpleScriptContext</code>: <br>
	 * <br>
	 * <ul>
	 * <li>Uses the specified <code>Bindings</code> for its <code>ENGINE_SCOPE</code></li>
	 * <li>Uses the <code>Bindings</code> returned by the abstract <code>getGlobalScope</code> method as
	 * its <code>GLOBAL_SCOPE</code></li>
	 * <li>Uses the Reader and Writer in the default <code>ScriptContext</code> of this
	 * <code>ScriptEngine</code></li>
	 * </ul>
	 * <br>
	 * <br>
	 * A <code>SimpleScriptContext</code> returned by this method is used to implement eval methods
	 * using the abstract <code>eval(Reader,Bindings)</code> and <code>eval(String,Bindings)</code>
	 * versions.
	 *
	 * @param nn Bindings to use for the <code>ENGINE_SCOPE</code>
	 * @return The <code>SimpleScriptContext</code>
	 */
	protected ScriptContext getScriptContext(Bindings nn) {

		SimpleScriptContext ctxt = new SimpleScriptContext();
		Bindings gs = getBindings(ScriptContext.GLOBAL_SCOPE);

		if (gs != null) {
			ctxt.setBindings(gs, ScriptContext.GLOBAL_SCOPE);
		}

		if (nn != null) {
			ctxt.setBindings(nn, ScriptContext.ENGINE_SCOPE);
		}
		else {
			throw new NullPointerException("Engine scope Bindings may not be null.");
		}

		ctxt.setReader(context.getReader());
		ctxt.setWriter(context.getWriter());
		ctxt.setErrorWriter(context.getErrorWriter());

		return ctxt;

	}
}
